The broad objective of the proposed research is to isolate, characterize and determine the molecular modes of action of toxic components of North American venoms. Not only will such knowledge aid specific treatment of envenomation, but these components may themselves be useful as therapeutic agents or scientific probes. The possible utility of isolated venom components will be investigated. The four venoms which are being studied in this project are those obtained from the timber rattlesnake, Crotalus horridus horidus, the eastern cottonmouth, Agkistrodon piscivorus piscivorus, the northern copperhead, Agkistrodon contortrix mokasen, and the brown recluse spider, Loxosceles reclusa. All four of these venoms produce severe local tissue responses while the systemic effects of the snake venoms are comparatively mild. We have developed assays and chromatographic techniques which allow the isolation of certain activities from all four venoms. Emphasis has been placed upon procuring those components which are responsible for the local and systemic effects these venoms cause in mammals. During the course of the proposed research the characterization of the following venom components will be completed: the primary basic and acidic hemorrhagins from timber rattlesnake venom, eastern cottonmouth venom, and the systemic effector from brown reculse venom. The site of action of the timber rattlesnake systemic toxin will be further investigated by utilizing labeled toxin. In addition, the mechanisms of the isolated procoagulants from northern copperhead and timber rattlesnake venoms will be investigated by fibrinopeptide analyses. The substrate specificities of the two northern copperhead phospholipases which have been purified to homogeneity will also be determined. Studies will continue on determining the source of the apparent neurotoxin found in one commercial preparation of northern copperhead venom.